Which of the following oxides, when added to water, will produce a solution with a pH greater than 7?
Show the answer and explanation
Correct answer
C. Na2O
Principle or equation
Metallic oxides (basic oxides) react with water to form bases, producing alkaline solutions (pH > 7). Nonmetallic oxides (acidic oxides) form acids, producing acidic solutions (pH < 7).
Why this answer is correct
Na2O is a basic oxide. It reacts with water: Na2O + H2O → 2NaOH, producing a strong base, so the solution is alkaline (pH > 7). SO2, CO2, and P2O5 are acidic oxides; they form acidic solutions (e.g., H2SO3, H2CO3, H3PO4) with pH < 7.
Example
For instance, CaO (basic oxide) gives Ca(OH)2 in water, which is basic. Similarly, Na2O gives NaOH.
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